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    • Thread Starter

    Can anyone help me with this question?

    Calculate the number of free electrons per metre length of wire if a current of 2.0A produces a drift velocity of 1.0 * 10^-3 ms^-1

    I know the answer but I don't understand the method on how to get to it.

    You have an equation for drift velocity, usually in the form

    I = nAqv

    In this equation, n is the nº of electrons per unit volume. You've been asked for nº per unit length.

    Suppose N is the total number so n = N/vol and Vol of course = length x area

    So n = N/(LxA) If you multipy both sides by A (or take the A to the other side)

    nA = N/L or in otherwords, nA = number of electrons per unit length.
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